1. Field of the Invention
The present invention relates to a magneto-optical layer utilizing a magneto-optical effect, particularly useful as a recording layer in a magneto-optical recording medium, and also relates to such a magneto-optical recording medium.
2. Description of the Related Art
Optical recording media have been widely investigated and developed as high density and large capacity information recording media. Particularly, since magneto-optical recording media can be repeatedly recorded on and erased and thus have wide applicable fields, various types of magneto-optical recording media have been proposed.
Heretofore, a laser beam having a wavelength of 830 nm has been usually used in most magneto-optical recording systems. Nevertheless, in future systems to attain a higher density recording, laser beams having a wavelength shorter than that of the laser beam currently used and ranging 400 to 550 nm are expected to be used.
Conventional magneto-optical recording media use a magneto-optical recording layer of amorphous rare earth-transition metal alloy such as TbFeCo having an easy magnetization axis perpendicular to the main surface of the layer. Nevertheless, these amorphous rare earth-transition metal alloy recording layers do not have an effective magneto-optical effect in the shorter wavelength range as above.
To attain a magneto-optical recording layer having a magneto-optical recording effect at such a shorter wavelength and a perpendicular magnetic anisotropy, Co/Pt multi-layers having a structure in which platinum and cobalt layers are alternately stacked have been vigorously investigated to make them practical to use. This Co/Pt multi-layer is however disadvantageous since it requires a complex process of formation due to a multi-layer structure, which significantly lowers productivity.
It is also well known that a CoPt binary alloy layer has excellent magneto-optical characteristics at the short wavelength (see, for example, K. H. J. Buschow et al., J. Magn. Mat., 38, 1(1983)).
This CoPt layer however is required to be deposited on a substrate heated to 200.degree. C. in electron beam evaporation method, in order to obtain a magneto-optical layer having a perpendicular magnetization anisotropy (C. J. Lin et al., Appl. Phys. Lett., 61, 1600 (1992)). This is disadvantageous in terms of productivity and further it is impossible to deposit such a magneto-optical recording layer on a plastic substrate such as a polycarbonate substrate used in current magneto-optical recording media.
The object of the present invention is therefore to provide a magneto-optical layer having a magneto-optical effect at a wavelength shorter than a wavelength currently used, the magneto-optical layer being able to be deposited at room temperature, without necessity of a complex process of production such as that for a multi-layer super lattice structure.